As oil and gas drilling and production techniques have advanced and become more complex and versatile, many different down-hole tools have come into use. Some include their own power packs, or other energy sources, and either are or can potentially be operated by remote control. Microprocessors, which are small, reliable and have a low power consumption, are commonly used in such tools and equipment. There are many other potential applications for remote control of tools and other equipment within a confining passageway at a substantial distance, including not only in the drilling, completion, workover, production and abandonment of a well, but also in tools and devices that are fixed or movable in pipelines and further with underwater equipment connected to a surface system via a subsea manifold. If commands can reliably be communicated to a remote well bore location, then such functions as opening and closing valves, sliding sleeves, inflating plugs, detonating perforating guns, shifting tools and setting packers are available. Through the use of remote actuation, expensive down time in the well can be minimized, saving the costs of many hours or even days of operation.
Systems have been proposed, and some are in use, for remote control of equipment in well bore installations. A wire connection system using electric line has been in use for some time, and remains in use today. This system employs a heavy duty electrical line that is fed into the well bore along the tubing or casing string to the down-hole location. The line is of relatively large diameter and for setup requires a massive carrier and support equipment, with setup time requiring many hours. Moreover, electrical power transmitted into a deep well creates potential dangers from short circuits and arcing in explosive environments at the well site where an inert atmosphere cannot be maintained. A later developed “Slickline” is only a wire for providing mechanical operations and is of much smaller diameter although very high strength. While it can be transported and manipulated by much smaller vehicles and installations, and is deployed considerably more rapidly than the electric line mechanism, it is not well suited to remote operation of down-hole tools. Time consuming and unsafe control methods with these systems are based on use of times, and motion sequences combined with, pressure and temperature readings.
Other systems are known for transmitting non-electrical commands to preinstalled down-hole tools by communicating through a pressurized liquid medium or metal walls along the well bore. Pressure variations imparted at the surface are sensed by a strain gauge or other transducer at the remote location, to trigger a battery powered device in response to a coded pressure varying signal. One such system, called the “EDGE” (trademark of Baker Hughes) system, interfaces with liquid media only and injects pulses of chosen frequency into the well bore. A down-hole tool having an actuable element powered at the tool includes electronic circuits which filter the selected frequency from other variations and respond to a selected pattern of pulse frequencies. This system requires substantial setup time and can only be used in a constant and predictable all-liquid bore. Another system effects control of mechanical devices by establishing a high initial pressure and then bleeding off pressure in a programmed fashion.
Another prior art system is disclosed in U.S. Pat. No. 3,227,228 (1966) assigned to Bannister. This patent teaches the use of a liquid injector to inject liquid into a liquid-filled well bore to create a pressure pulse. The pressure pulse travels down the liquid-filled tubing and is detected as it passes a pressure transducer projecting out into the fluid. The signal from the pressure transducer is used to actuate a downhole tool. As with the Baker “EDGE” system, the conduit through which the pulse is to be sent has to be completely filled with liquid for the system to work.
There is a need, therefore, for a remote control system and method which will function reliably in actuating a remote tool or other equipment, whatever the nature of the media in the confining elongated bore. Preferably, it should be useful in a wide range of well drilling and completion operations, including MWD, and in pipeline applications which are generally horizontal. The system and method should ensure against accidental triggering of the remote device and be essentially insensitive to extraneous operating conditions and effects. It should also be capable of remote control of selected individual ones of a number of different devices, and providing redundant modes of detection for enhanced reliability and communication capability. While retaining the higher degree of reliability, the system should preferably also require substantially less setup and operating time for field installation and actuation.
MWD installations currently in use require communication with bottom hole assembly (BHA) measuring equipment such as sensors, instruments and microprocessors. The MWD equipment stores information on many parameters including but not limited to bit direction, hole angle, formation evaluation, pressure, temperature, weight on bit, vibration and the like. This is transmitted to the surface using mud pulsing technology. Communicating to the MWD equipment for the purpose of controlling movable elements (i.e., to adjust the stabilizer blades to control direction) is, however, another matter, since not only must commands be given, they must actuate the proper tool and provide sufficient data to make a quantitative adjustment. The current methods use changes of pump rate, and changes of weight on the bit, both of which take time, are limited in data rate, and increase the chances of sticking the drill string.
Remote control of elements in pipelines is a significant objective, since pipeline pigs are driven downstream for inspection or cleaning purposes and can stick or malfunction. Some pigs include internal processor and control equipment while others are designed to disintegrate under particular conditions. The ability to deliver commands to a pig or a stationary device in a remote location in a pipeline is thus highly desirable.